> Just because you don't understand the difference between a penalty and an incentive doesn't make your analogy suddenly correct.
There is no difference between a tax penalty and a tax incentive (more precisely, a tax incentive is exactly identical to a general tax cut plus a tax penalty for everyone who doesn't qualify for the incentive, and a tax penalty is equivalent to a general tax increase plus a tax incentive for everyone not subject to the penalty; so, except as concerns the general level of taxation, penalties are exactly the same as incentives.)
> If you don't own a mortgage, you cannot be fined into the negative
Since having a mortgage or not can make the difference between owing net income taxes or not, if you have $0 net worth before a particular year's taxes are considered, you absolutely can be "fined into the negative" for not paying interest on a mortgage (lenders, not borrowers, own mortgages.)
There is no difference between a tax penalty and a tax incentive (more precisely, a tax incentive is exactly identical to a general tax cut plus a tax penalty for everyone who doesn't qualify for the incentive, and a tax penalty is equivalent to a general tax increase plus a tax incentive for everyone not subject to the penalty; so, except as concerns the general level of taxation, penalties are exactly the same as incentives.)
> If you don't own a mortgage, you cannot be fined into the negative
Since having a mortgage or not can make the difference between owing net income taxes or not, if you have $0 net worth before a particular year's taxes are considered, you absolutely can be "fined into the negative" for not paying interest on a mortgage (lenders, not borrowers, own mortgages.)